1. Field of the Invention
The present invention relates to a liquid droplet jetting apparatus which includes a liquid droplet jetting head, and a liquid droplet jetting state inspection unit which inspects liquid droplet jetting state of the liquid droplet jetting head.
2. Description of the Related Art
An apparatus which includes a unit for inspecting liquid droplet jetting state of a nozzle has hitherto been known as a liquid droplet jetting apparatus which includes a liquid droplet jetting head having a plurality of nozzles.
For instance, a unit which inspects liquid droplet jetting state of an ink jet head of an ink jet recording apparatus has been disclosed in US Patent Application Publication No. 2010/0079535 (corresponds to Japanese Patent Application Laid-open No. 2010-76361). The inspection unit in the US Patent Application Publication No. 2010/0079535 has a vibration plate facing nozzle openings of the ink-jet head, and a piezoelectric element which is joined to the vibration plate, and vibration (deformation) of the vibration plate, which is generated when droplets of ink are landed, is converted to a voltage signal by the piezoelectric element. Consequently, it is possible to inspect whether or not there is misjetting in the nozzle, based on an output voltage of the piezoelectric element.
As a jetting defect of a nozzle, in addition to a defect in which liquid droplets are not at all jetted (misjetting), there is also a detect in which the liquid droplets are jetted from the nozzle but the jetting direction of the nozzle is inclined with respect to a regular (normal) direction (also called as inclined jetting). When the jetting is inclined, landing position of droplets is deviated from the original position. Therefore, it is preferable that the inclined jetting is also detected similarly as misjetting.
However, in the inspection apparatus in US Patent Application Publication No. 2010/0079535, although it is possible to detect whether or not the ink droplets are landed on the vibration plate from a change in the output voltage of the piezoelectric element, it is not possible to detect accurately as to at which position of the vibration plate the liquid droplets have landed. Accordingly, it is not possible to detect inclined jetting by comparing the actual landing position with the original landing position when there is no inclined jetting.